Species Of Arthrobotrys Research Articles

Assessing the In Vitro Individual and Combined Effect of Arthrobotrys oligospora and A. musiformis (Orbiliales) Liquid Culture Filtrates against Infective Larvae of the Sheep Blood-Feeding Nematode Haemonchus contortus (Trichostrongylidae).

Arthrobotrys species are nematophagous fungi that secrete extracellular nematocidal products (ECP). The individual and combined effects of ECP from Arthrobotrys oligospora (Ao) and A. musiformis (Am) growth in liquid media against Haemonchus contortus L3 (HcL3) were assessed. The isolation, morphological (MI) and molecular identification (Mol-I), assessment of nematocidal activity (NA) of fungal liquid culture filtrates (LCF) in two liquid media alone and in combination and the myco-compound profile identification (MCP) were performed. The MI suggested that the fungi corresponded to the species Ao and Am. This result was confirmed by PCR analysis followed by sequencing, alignment and a phylogenetic analysis. Likewise, the highest Hc mortalities were 91.4% with individual LCF of Am and 86.2% with those of Ao at the highest concentration (100 mg/mL) in Czapek-Dox Broth. The combination of both LCF resulted in a similarly high larval mortality with no statistical differences in relation to individual activity (p > 0.05). The MCP showed the presence of alkaloids in both fungi. Coumarins, sterols and saponins were found only in Ao. Both fungi produced ECP with a high NA that could be identified and assessed in future studies as potential natural anthelmintic compounds.

Isolation, Identification, and Evaluation of the Predatory Activity of Chinese Arthrobotrys Species towards Economically Important Plant-Parasitic Nematodes.

The current investigation aimed to isolate and identify predatory fungal strains and evaluate their efficacy in mitigating the effects of plant-parasitic nematodes. We successfully isolated three distinct nematophagous fungal strains from soil samples, identified as Arthrobotrys megalosporus, A. oligospora, and A. sinensis, using conventional and molecular identification methodologies. In vitro trials illustrated the high capture efficiency of these fungi against plant-parasitic nematodes. Over an exposure period of 48 h to Aphelenchoides besseyi, Bursaphelenchus xylophilus, and Ditylenchus destructor, A. megalosporus (GUCC220044) displayed predation rates of 99.7%, 83.0%, and 21.1%, respectively. A. oligospora (GUCC220045) demonstrated predation rates of 97.3%, 97.3%, and 54.6%, and A. sinensis (GUCC220046) showed rates of 85.1%, 68.3%, and 19.0% against the same cohort of nematodes. The experimental outcomes substantiate that all three identified fungal strains demonstrate predatory activity against the tested nematodes, albeit with varying efficiencies.

Conidia Fusion: A Mechanism for Fungal Adaptation to Nutrient-Poor Habitats.

Conidia fusion (CF) is a commonly observed structure in fungi. However, it has not been systematically studied. This study examined 2457 strains of nematode-trapping fungi (NTF) to explore the species specificity, physiological period, and physiological significance of CF. The results demonstrated that only six species of Arthrobotrys can form CF among the sixty-five tested NTF species. The studies on the model species Arthrobotrys oligospora (DL228) showed that CF occurred in both shed and unshed plus mature and immature conidia. Additionally, the conidia fusion rate (CFR) increased significantly with the decrease of nutrient concentration in habitats. The studies on the conidia fusion body (CFB) produced by A. oligospora (DL228) revealed that the more conidia contained in the CFB, the faster and denser the mycelia of the CFB germinated in weak nutrient medium and soil plates. On the one hand, rapid mycelial extension is beneficial for the CFB to quickly find new nutrient sources in habitats with uneven nutrient distribution. On the other hand, dense mycelium increases the contact area with the environment, improving the nutrient absorption efficiency, which is conducive to improving the survival rate of conidia in the weak nutrient environment. In addition, all species that form CF produce smaller conidia. Based on this observation, CF may be a strategy to balance the defects (nutrient deficiency) caused by conidia miniaturization.

Arthrobotrys blastospora sp. nov. (Orbiliomycetes): A Living Fossil Displaying Morphological Traits of Mesozoic Carnivorous Fungi.

The evolution of carnivorous fungi in deep time is still poorly understood as their fossil record is scarce. The approximately 100-million-year-old Cretaceous Palaeoanellus dimorphus is the earliest fossil of carnivorous fungi ever discovered. However, its accuracy and ancestral position has been widely questioned because no similar species have been found in modern ecosystems. During a survey of carnivorous fungi in Yunnan, China, two fungal isolates strongly morphologically resembling P. dimorphus were discovered and identified as a new species of Arthrobotrys (Orbiliaceae, Orbiliomycetes), a modern genus of carnivorous fungi. Phylogenetically, Arthrobotrys blastospora sp. nov. forms a sister lineage to A. oligospora. A. blastospora catches nematodes with adhesive networks and produces yeast-like blastospores. This character combination is absent in all other previously known modern carnivorous fungi but is strikingly similar to the Cretaceous P. dimorphus. In this paper, we describe A. blastospora in detail and discuss its relationship to P. dimorphus.

Identification, Characterization, and Evaluation of Nematophagous Fungal Species of Arthrobotrys and Tolypocladium for the Management of Meloidogyne incognita.

Root-knot nematodes belonging to the genus Meloidogyne are agriculturally important pests, and biocontrol strategies offer safer alternatives for their management. In the present study, two fungal species from Indian soils were identified as Arthrobotrys thaumasia and Tolypocladium cylindrosporum based on morphological characteristics and further confirmed using molecular markers. In vitro evaluation of A. thaumasia against M. incognita and Caenorhabditis elegans showed 82 and 73% parasitism, respectively, whereas T. cylindrosporum gave 65.2 and 57.7% parasitism, respectively. Similarly, culture filtrates of A. thaumasia caused 57.7 and 53.7% mortality of M. incognita and C. elegans, respectively, whereas T. cylindrosporum caused higher mortality of 87.3 and 64%, respectively. Besides, greenhouse evaluation of both fungi against M. incognita infecting tomato significantly reduced nematode disease burden reflecting parasitic success measured as the total number of galls, egg masses, eggs per egg mass, and derived nematode multiplication factor. Application of A. thaumasia and T. cylindrosporum reduced nematode multiplication factor by 80 and 95%, respectively, compared with control. General metabolite profiling of tested fungi using gas chromatography–mass spectrometry and ultra-performance liquid chromatography–quadrupole/time of flight mass spectrometry reported for the first time here showed presence of various volatile and non-volatile compounds with nematicidal activity, viz., trimethyl-heptadiene, methyl-hexadecanol, dodecadienal, decane, terpendole E, dodecane, acetamido-6-anthraquinone, and hexadecanol. Also, other compounds such as undecane, dibutyl-disulfide, octadecenal, paganin, talathermophilin, dactylarin, tolypyridone A, tolypyridone B, pyridoxatin, and destruxin were identified, reported in the literature to possess antibacterial, antifungal, and insecticidal properties. This is the first report of the occurrence of both fungi from India and pioneer demonstration of T. cylindrosporum for root-knot nematode management.

Taxonomic and biological characterization and predatory activity of four nematophagous fungi isolates of Arthrobotrys species from Tapachula, Chiapas, Mexico

ABSTRACT A batch of nematophagous fungi (NF), isolated from soil and animal faeces at Tapachula, Chiapas, Mexico, was identified through morphological methods and molecular tools. Additionally, the fungi were biologically characterised through their in vitro predatory capability against the free-living nematode Panagrellus redivivus. Molecular identification of nine isolates was achieved by amplifying the 18S, 5.8S and 28S regions using ITS5 and ITS4 oligonucleotides, followed by sequencing and aligning through BLAST. Only species of Arthrobotrys genus: A. oligospora, A. conoides, A. arthrobotryoides and A. musiformis were found. The in vitro bioassay revealed a large variability in the predatory capabilities of the different isolates. The isolate Z1-1-2 of A. arthrobotryoides showed the highest nematode reduction (NR) from 822.8 (± 169.5) to only 51.4 (± 35.2) = 93.7% NR; in contrast A. oligospora (isolate Z3-2-2) showed the lowest NR from 548.5 (± 66.6) to 234.2 (± 123.6) = 57.2% Genotyping analysis corroborated the morphological identification. The comparison of sequences with the NCBI sequences showed a close phylogenetic relationship. A phylogenetic tree was generated to compare its phylogenetic relationship with other strains reported in the NCBI. The NF isolated could be potential candidates for future studies on the biological control of nematodes.

Natural diversity in the predatory behavior facilitates the establishment of a robust model strain for nematode-trapping fungi

Nematode-trapping fungi (NTF) are a group of specialized microbial predators that consume nematodes when food sources are limited. Predation is initiated when conserved nematode ascaroside pheromones are sensed, followed by the development of complex trapping devices. To gain insights into the coevolution of this interkingdom predator-prey relationship, we investigated natural populations of nematodes and NTF that we found to be ubiquitous in soils. Arthrobotrys species were sympatric with various nematode species and behaved as generalist predators. The ability to sense prey among wild isolates of Arthrobotrys oligospora varied greatly, as determined by the number of traps after exposure to Caenorhabditis elegans While some strains were highly sensitive to C. elegans and the nematode pheromone ascarosides, others responded only weakly. Furthermore, strains that were highly sensitive to the nematode prey also developed traps faster. The polymorphic nature of trap formation correlated with competency in prey killing, as well as with the phylogeny of A. oligospora natural strains, calculated after assembly and annotation of the genomes of 20 isolates. A chromosome-level genome assembly and annotation were established for one of the most sensitive wild isolates, and deletion of the only G-protein β-subunit-encoding gene of A. oligospora nearly abolished trap formation. In summary, our study establishes a highly responsive A. oligospora wild isolate as a model strain for the study of fungus-nematode interactions and demonstrates that trap formation is a fitness character in generalist predators of the nematode-trapping fungus family.

Epigenetic Manipulation Induces the Production of Coumarin‐Type Secondary Metabolite from Arthrobotrys foliicola

AbstractPursuing epigenetic manipulation approach in fungi led to the isolation of an unusual coumarin metabolite from fungi. An addition of the histone deacetylase inhibitor, suberohydroxamic acid (SBHA), to the culture medium of Arthrobotrys foliicola induced production of the coumarin‐type secondary metabolite represented by a single intensive peak in the HPLC profile of the ethyl acetate extract. The compound which was identified as 4‐ethyl‐7‐hydroxy‐8‐methyl‐2H‐chromen‐2‐one (1) was isolated from nature for the first time. Moreover, the investigation on the remaining part of the HPLC profile led to the separation of 6‐ethyl‐2,4‐dihydroxy‐3‐methylbenzaldehyde (2) and ten 2,5‐diketopiperazine compounds (3–12). The structures of isolates were deduced by their mass and NMR spectroscopic data. The coumarin‐type secondary metabolite (1) with peculiar smell induced by epigenetic stimulation is found for the first time in the Arthrobotrys species and the family Orbiliaceae. We evaluated 1 for the cytotoxic, anti‐inflammatory, anti‐allergic and nematocidal activities, however, it was found inactive.

Screening of different sample types associated with sheep and cattle for the presence of nematophagous fungi in China.

A total of 1502 samples, including feces of sheep (793) and cattle (348), pasture soil (118), dung compost (147) and barn soil (96), were examined between October 2012 and August 2014 to discover potential strains of nematophagous fungi for the biological control of livestock-parasitic nematodes. These samples were collected from 87 sites located in 48 counties of 20 provinces (autonomous regions/municipalities) of China. Fungi were identified down to a species level. Four hundred and seventy-seven isolates, which were distributed in 8 genera and 28 taxa, were identified as nematophagous fungi. Nematode-trapping fungi included 17 species and one unidentified species of Arthrobotrys, two of Dactylella, Drechslerella dactyloides, and Duddingtonia flagrans. Five identified species and two unidentified species of endoparasitic fungi were isolated. The predominant species from all regions were Arthrobotrys oligospora, followed by Arthrobotrys musiformis, Arthrobotrys (Monacrosporium) thaumasiun, and Arthrobotrys (Monacrosporium) microscaphoides. Species with adhesive networks were the most frequently isolated. Among the endoparasitic fungi, Podocrella harposporifera (Harposporium anguillulae) was the most common species, followed by Harposporium lilliputanum and Harposporium arcuatum. Based on Shannon diversity index, the diversity levels of nematophagous fungi were relatively higher in samples associated with cattle, barn soil, and subtropical monsoon climate zone. Three species isolated from this study, namely, Duddingtonia flagrans, Arthrobotrys salina (Monacrosporium salinum), and Arthrobotrys oligospora var. sarmatica, are newly recorded in China, and 20 species (including one unidentified species) are newly recorded in sheep and cattle barn soils worldwide.

Arthrobotrys xiangyunensis, a novel nematode-trapping taxon from a hot-spring in Yunnan Province, China

An Arthrobotrys species with adhesive nets (trapping device) was isolated from hot-spring waterlogged soil during research on evolutionary patterns of nematode-trapping fungi in Yunnan Province, China. Morphological and phylogenetic analyses indicate this is a novel predatory species of Arthrobotrys, which we herein introduce as A. xiangyunensis. The new species is characterized by occasionally branched conidiophores, colorless, fusiform to oval or clavate conidia which mostly have 1–5 septa and measure 27–72(55.8) × 14.5–28.5(21.9) μm. The new species is introduced with illustrations in this paper. Its morphology is rather similar to Monacrosporium guizhouense, M. longiphorum, M. sphaeroides, M. eudermatum and Arthrobotrys mangrovispora, but the phylogenetic analysis shows that A. xiangyunensis and its morphological relatives are distinct.

English

Arthrobotrys javanica captures nematodes in adhesive networks. This fungus was isolated from the soil around the root of Dystaenia takeshimana in Ulleung Island, South Korea. It produces 1-septate conidia with a size of 31.1 × 12.0 µm on a candelabrum-like apical branch. This feature distinguishes A. javanica from other species of Arthrobotrys. Chlamydospores were observed (d = 17 µm), which were not previously mentioned in the original description. The present study is the first report on A. javanica in Korea.   Key words: Arthrobotrys javanica, nematode-trapping fungus, adhesive network.

Differential susceptibility of entomopathogenic nematodes to nematophagous fungi from Florida citrus orchards

AbstractLaboratory experiments were conducted to study the effects of various trapping and endoparasitic nematophagous fungi (NF) isolated from Florida citrus orchards on five entomopathogenic nematode (EPN) species that show various distributions across Florida's citrus industry. Four trapping NF (Arthrobotrys oligospora, A. dactyloides, A. musiformis and Gamsylella gephyropaga) and two endoparasitic NF (Catenaria sp. and Myzocytium sp.) were tested against Steinernema diaprepesi (Sd), S. glaseri (Sg), S. riobrave (Sr), Heterorhabditis zealandica (Hz) and H. indica (Hi). Fungi were added to soil microcosms either as a pure culture on agar plugs (trapping NF) or as fungal-colonised nematodes (endoparasitic NF) on agar plugs, concurrently with 2000 EPN of a given species. After 7 or 14 days exposure, nematodes were recovered from the soil using Baermann funnels. The recovery of all EPN species was reduced between 56-92% by G. gephyropaga. Neither Sd or Sg were affected by any species of Arthrobotrys, whereas A. musiformis reduced recovery of all other EPN and A. oligospora reduced numbers of all other species except Hi. Both endoparasitic NF reduced the recovery of all EPN except Hi by at least 82%. The data are consistent with the hypothesis that NF may play a role in regulating regional patterns of abundance and diversity of EPN species in Florida, which in turn regulate the abundance of a major citrus pest, the Diaprepes root weevil, Diaprepes abbreviatus.

선충포획성 Arthrobotrys속균에 의한 소나무재선충 포획 특성

Arthrobotrys속 균은 불완전균으로 토양선충을 포획하는 살선충 곰팡이다. 본 논문에서는 선충포획성 균종인 A. oligospora, A. dactyloides, A. conoides의 균사생장, 선충 포획기작의 특성, 그리고 소나무재선충에 대한 감염능력을 이해하여 살선충 효과가 높은 균종을 알고자 하였다. 소나무재선충은 잿빛곰팡이(Botrytis cinera)에 접종해 증식시켰으며 여기에 Arthrobotrys속 3종 각각의 균사배양체 <TEX>$1\;cm^2$</TEX>씩 접종하고 배지, 온도, pH, 소나무재선충 접종밀도, 영양조건이 균사의 생장에 미치는 영향을 측정하였다. 그 결과 전체적으로 A. conoides의 생장이 가장 빨랐으며(13.9 mm/day, PDA) A. dactyloides가 가장 느렸다(3 mm/day, PDA). 3가지 균의 생장은 PDA배지, <TEX>$25^{\circ}C$</TEX>, pH 4.5의 조건에서 가장 양호하였다. A. conoides 균과 A. oligospora 균은 500마리의 재선충 접종으로 생장이 촉진됐으나, 10,000마리 접종으로는 느려졌다. A. dactyloides는 산성에서 생장하지 않았으며 재선충이 많을수록 더 느렸다. A. conoides와 A. oligospora의 선충포획기관은 균사보다 굵은 고리들의 망상 구조로서 선충 존재시만 형성되었으나, A. dactyloides의 포획기관은 단일한 원모양으로 선충이 없어도 형성되었다. A. conoides가 A. oligosora보다 포획기관 형성이 빨랐으며, 재선충 포획 후 균사가 재선충 내부로 침입하여 작고 많은 침입구(infection bulb)를 만들고 선충을 소화하였다. 그러나 A. dactyloides는 포획기관의 수가 적었고 포획도 하지 못하였다. A. conoides의 재선충 감염율은 95%였고, A. oligospora의 감염율은 80%였다. 그리고 위 두 균의 조합접종에 의한 선충감염율은 92%였다. 그러나 A. dactyloides는 오히려 재선충의 밀도를 증가시켰다. A. conoides 균은 빠른 생장률과 초기 포획으로, A. oligospora는 균밀도를 증가시켜서 재선충 감염율을 높였다. 결론적으로 A. conoides균은 균사생장률과 재선충감염율이 높으므로 소나무재선충의 생물학적 방제에 이용될 수 있을 것이라 생각한다. Pinewood nematode (PWN) trapping by nematophagous fungi, Arthrobotrys conoides, A. dactyloides and A. oligospora and the fungal growth were characterized. The three Arthrobotrys species each was inoculated into the PWN cultured on Botrytis cinera fungal colony on potato dextrose agar (PDA). The effects of temperature, pH, PWN inoculation density and nutrients on the growth of the three Arthrobotrys spp were measured. A. conoides grew fast, 13.9 mm/day while A. dactyloides grew slow, 3 mm/day. PDA medium was the best for the fungal growth at <TEX>$25^{\circ}C$</TEX> and pH 4.5. The Arthrobotrys spp growth was stimulated by 500 nematodes inoculation but not by 1000 inoculation. A. dactyloides did not grow below pH 4.5 and at high PWN density. A. conoides and A oligospora formed trapping organs with thick constricting hyphal network only when PWN present, while A. dactyloides formed the organ with circular hyphae constitutively. A. conoides formed trapping organs faster than A. oligospora did. The nematode trapping hyphae of the fungi penetrated into PNW inside to form many tiny infection bulbs and to digest the nematode. However, A. dactyloides formed a few trapping organs but no trapping was observed. Infection rate of PWN was 95% by A. conoides, 80% by A. oligospora and 92% by the combination inoculation of A. conoides and A. oligospora. In contrast A. dactyloides increased PWN density without infecton. There was no interaction effect in any combination inoculation of the three Arthrobotrys spp. A. conoides enhanced PWN infection rate by rapid hyphal growth and early trapping, while A. oligospora did it by increasing hyphal density. In conclusion A. conoides is the most effective in both hyphal growth and infection, and thus these characteristics can be utilized as a biological control of PWN.

Observations on the occurrence of nematophagous fungi in Scotland

A total of 54 nematophagous fungi were isolated from soil samples from 4 different types of habitats in Edinburgh, Scotland. Nematode-trapping fungi included 11 species of Arthrobotrys, 2 each of Dactylellina and Drechslerella and 3 of Stylopage. Fifteen species of endoparasites were isolated. The highest frequency of occurrence in terms of habitat was of Arthrobotrys gephyropaga and Drechslerella brochopaga among predators and that of Harposporium anguillulae among endoparasites. This study indicates equal distribution of both predatory and endoparasitic fungi.

Occurrence, morphological characteristics and ribotyping of New Zealand isolates of Duddingtonia flagrans, a candidate for biocontrol of animal parasitic nematodes

The nematophagous fungus Duddingtonia flagrans has shown potential for biological control of nematode parasites of livestock in several countries. A survey for the presence of D. flagrans in New Zealand was undertaken in 1997–98 on 24 farm, research, and domestic properties in the southern North Island. The nematophagous fungi found on isolation plates included species of Arthrobotrys, Dactylellina, Nematoctonus, Harposporium, and Duddingtonia. Isolates that produced the three‐dimensional nets and abundant chlamydospores, characteristic of D. flagrans, were detected in 6 of 205 samples examined. The fungus was obtained from a variety of substrates such as cattle dung, horse dung, seepage from a silage pit, and decomposing lawn clippings. Morphological characteristics, and the sequences of ITS/5.8 region of ribosomal DNA, were very similar to those published for D. flagrans. The fungus was re‐isolated from the faeces of lambs 16–40 h after they had been dosed orally with chlamydospores, indicating survival of gut passage.

Microbial diversity during maturation and natural processing of coffee cherries of Coffea arabica in Brazil

The magnitude and diversity of the microbial population associated with dry (natural) processing of coffee ( Coffea arabica) has been assessed during a 2-year period on 15 different farms in the Sul de Minas region of Brazil. Peptone water-washed samples were taken of maturing cherries on trees (cherries, raisins and dried cherries) and from ground fermentations. The microbial load varied from 3×10 4 to 2.2×10 9 cfu/cherry with a median value of 1.6×10 7 cfu/cherry. The microbial load increased after heavy rainfall on cherries that were drying on the ground. At all stages, bacteria were usually the most abundant group, followed by filamentous fungi and finally yeasts. Counts of bacteria, yeasts and fungi varied considerably between farms and at different stages of maturation and processing and no consistent pattern could be seen. Yeasts showed an increase during the fermentation process. Median counts were not significantly different for fungi, yeasts and bacteria between the 2 years although Gram-negative bacteria dominated in the wet year and Gram-positive bacteria dominated in the dry year. Of a total of 754 isolates, 626 were identified to at least genus level comprising 44 genera and 64 different species. The 164 isolates of Gram-negative bacteria included 17 genera and 26 species, the most common of which were members of the genera Aeromonas, Pseudomonas, Enterobacter and Serratia. Of 191 isolates of Gram-positive bacteria, 23 were spore-forming and included six Bacillus species, and 118 were non-spore-formers of which over half were Cellulomonas with lesser numbers of Arthrobacter, Microbacterium, Brochothrix, Dermabacter and Lactobacillus. Of the 107 yeast isolates, 90 were identified into 12 genera and 24 different species and almost all were fermentative. The most common genera, in decreasing frequency, were Pichia, Candida, Arxula and Saccharomycopsis. There were many rarely described yeasts including Pichia lynferdii and Arxula adeninivorans. Almost all 292 fungal isolates were identified to genus level and 52 were identified to species level. Cladosporium, Fusarium and Penicillium each comprised about one third of the isolates and were found on all farms. Only 3% of the isolates were Aspergillus. Beauvaria, Monilia, Rhizoctonia and Arthrobotrys species were also occasionally found. The microbial flora is much more varied and complex than found in wet fermentations. The genera and species identified include members known to have all types of pectinase and cellulase activities.

Arthrobotrys hertziana sp. nov. from the Canary Islands

A new nematophagous hyphomycete is described from the Canary Islands as Arthrobotrys hertziana. It has branched conidiophores with slightly swollen tips, mostly three-septate conidia, and sticky knobs as trapping devices. A key to Arthrobotrys species forming sticky knobs is presented. Among six nematode and two springtail species tested as hosts only the nematode Panagrellus redivivus was trapped. The results are discussed with reference to taxonomical problems and the possibly limited host range.

Effect of different west african species and strains ofArthrobotrys nematophagous fungi onMeloidogyne species

Different species ofArthrobotrys nematophagous fungi and several strains ofA. oligospora have been studied for their antagonistic effects against nematodes of the genusMeloidogyne, important pests of vegetables. All fungi trappedM. mayaguensis andM. incognita juvenilesin vitro but had no effect on the juveniles ofM. javanica. In pot experiments withM. mayaguensis, all fungi reduced the nematode populations and stimulated the growth of tomato seedlings. In a field trial, a strain of A.oligospora, isolated in Senegal and incorporated into compost blocks, was efficient in increasing the tomato seedling growth. The introduction of nematophagous fungi in compost blocks as a biological biocontrol technique against phytophagous nematodes adapted for developing countries is discussed.

A new species of Arthrobotrys from China

Arthrobotrys obovata sp. nov., a hyaline hyphomycete capturing and consuming nematodes on adhesive networks recovered from forest soil, is described. It is characterized by single or branched, erect, hyaline septate conidiophores, with denticle nodes on conidiophores which bear 5–15 obovoid, 1-septate conidia in loose capitate arrangement. The differences between A. obovata , and A. cystosporia, A. perpasta are tabulated and illustrated.

Identification of nematode-trapping fungi using RFLP analysis of the PCR-amplified ITS region of ribosomal DNA

Six isolates of Arthrobotrys oligospora var. oligospora , identified by morphological characters were screened for polymorphism in the ITS region of the ribosomal DNA. RFLPs produced with four different endonucleases were identical for five out of six isolates. The RFLP patterns were also compared to those from the ITS regions of other Arthrobotrys species as well as to other nematophagous fungi. All species tested produced unique RFLP patterns which could be distinguished from each other easily. The results suggest this method to be a good tool for fast identification of large numbers of isolates in screening assays. Only minute colonies are needed since enough amplification product could be obtained from 0·1 ng of total genomic DNA. The method can also be useful in verifying the true identity of isolates which are difficult to type morphologically.